Paul I have a little side project I am designing in the form of a rocket stove mass/hydronic heating system. The stove's J tube is assembled from 2300 degree firebrick with an 8" stainless stove pipe housing with rock wool insulation and a 20 gallon air compressor tank for the dome and external stove encasement. The top of the J tube is where gases can reach 800-1500 deg F and I would like to defend the compressor tank cap with an iconel shield.

My question is how thick do you think I need...or do I need it at all?

https://www.youtube.com/watch?v=-rcJ_lp-bYI